Self-cleaning digging wheel buckets



May 13, 1958 F. F. KOLBE 2,834,127

SELF-CLEANING DIGGiNG WHEEL BUCKETS Filed May 16, 1956 5 Sheets-Sheet 1 May 13, 1958 F. F. KOLBE SELFZCLEANING DIGGING WHEEL BucKE'rs 5 Sheets-Sheet 2 Filed May 16. 1956 May 13, 1958 Filed May 16. 1956 F. F. KOLBE SELF-CLEANING DIGGING WHEEL BUCKETS 5 Sheets-Sheet 3 May 13, 1958 F. F. KOLBE SELF-CLEANING meme WHEEL BUCKETS Filed May 16, 1956 5 sheets -sheet 4 United States Patent SELF-CLEANHNG DIGGING WHEEL BUCKETS Frank F. Kolhe, Winnetka, 11]., assignor to The United Electric Coal Companies, Chicago, 11]., a corporation of Delaware Application May 16, 1956, Serial No. 585,335

11 Claims. (Cl. 37189) The present invention relates to wheel excavators of the bucket type, and particularly, to improved buckets therefor. This application is a continuation-in-part of my co-pending, now abandoned, application, Serial No. 312,517, filed October l, 1952.

In use of a wheel excavator, the wheel is rotated to force the buckets at its periphery into the earth to scoop up earth materials, to carry the material upwardly and to discharge the material by gravity adjacent the top point of bucket rotation. However, earth sticks to and in conventional buckets, there being a steady build-up of dry earth, and a rapid accumulation of mud, clay and the like on the bucket surfaces, which decreases capacity and eventually renders the buckets useless. It has been necessary therefore to discontinue wheel operation at frequent intervals to clean conventional buckets manually.

Shut-down of wheel excavators is exceedingly expensive. For example, an excavator in use by the assignee of the application is 360 feet long, 160 feet tall and 35 feet wide, and includes a wheel 20 feet in diameter carrying eight buckets.

Excavator cost is estimated to be $60.00 per hour, and its capacity when the buckets are clean is about 1200 cubic yards per hour. The machine was designed for the removal of overburden in the order of 75-100 feet in the strip mining of coal, particularly the overburden from the surface down to about 25-35 feet above the coal seam, the last 25-35 feet being removed by a power shovel. Due to the steadily increasing ratio of overburden to coal vein thickness, coal removal today is approximately four to five times faster than overburden removal. Thus, if a coal stripping crew is to work an eight hour shift five days a week, the excavator must work 24 hours per day seven days a week. Shut-down of the wheel excavator will result in idling the shovel and the coal stripper and their crews.

With conventional buckets, the capacity of the wheel excavator described was considerably less than that indicated due to accumulation of earth on the bucket surfaces. Specifically, when earth accumulation reduced bucket capacity by about one-third, it was necessary to stop the wheel and clean the buckets manually. Average operating capacity thus was about one-sixth less than above indicated, or 1,000 cubic yards per hour, and shut-down time for cleaning was 50 to 60 hours per month. As to the excavator alone, decreased average capacity and shutdown time resulted in a monthly production loss of about 156,000 cubic yards of overburden, or the equivalent of about 130 hours of efficient excavator operation. To this must be added the loss of coal production. Due to these factors, the inefiiciency of conventional buckets resulted in a monthly loss of over $20,000.00-a quarter-million dollars per year.

The object of the present invention is to provide improved buckets for wheel excavators which are automatically self-cleaning, highly efficient and materially reduce the cost of overburden removal, and thus the cost of coal production.

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Another object of the invention is the provision of an improved self-cleaning bucket which automatically prevents excess accumulation of earth on the bucket surfaces and discharges its full load'of earth on each rotation of the wheel, thus constantly maintaining peak bucket capacity and eliminating shut-down time for cleaning, whereby the losses attendant upon conventional buckets are eliminated.

According to the invention, I provide an improved bucket for excavator wheels having at least the majority of the rear or back wall thereof defined by a flexible and movable mat. Specifically, the invention provides a selfcleaning bucket comprising spaced parallel side walls, narrow lip and tail portions joining the peripheral edges of the side Walls at the leading and trailing edges thereof, and a chain mat pivotally mounted solely at its forward and rearward edges on said lip and tail portions to constitute the back wall of the bucket. The mat is longer than the shortest distance between its pivotal mountings to conform generally to the arcuate curvature of a conventional back wall when the bucket is loaded, and the width of the mat is less than the distance between the side walls to accommodate gravitation of the mat into the bucket when the bucket is disposed in discharging position.

By virtue of the perforate structure of the mat, earth in descending out of the bucket cannot create a retarding suction force. Adherence of earth to the mat is not detrimental, since the mat moves with the material.

Moreover, in its movement, the mat effects a scraping action relative to the side walls to prevent excessive build up of earth thereon. The mat is flexible in all directions and responsive to wheel vibration to break up and discharge earth from the bucket. In particular, as the bucket approaches its discharging position, the central portion of the mat gravitates a substantial distance into the bucket and, due to its weight, attains substantial momentum. Suddenly, it is stopped short at its limit of movement and rebounds sharply upwardly, shaking itself, automatically to remove earth therefrom.

An important object of the invention is to provide an improved installation for the chain mat such that the same is freely spaced from and does not overlie or underlie any part of the remainder of the bucket. This assures free movement of the mat to gravitate into the bucket, and to flex and sway radially outwardly relative to the side walls to enhance the self cleaning function and to assume the most suitable contour for carrying the material thereon. Also, it eliminates the possibility of the mat bearing upon and being confined against a bucket surface by excavated earth. There are no mating surfaces between the bucket walls and mat onto which earth can become packed to render the mat ineffective. The mat is fully movable during each wheel rotation in the manner described to aiford the stated advantages, particularly to render the bucket self-cleaning, maintain peak capacity, and eliminate shut-down time for cleaning, whereby the cost of overburden removal is appreciably reduced.

A further object of the invention is the provision of a self-cleaning bucket for wheel excavators not subject to the design limitations of conventional buckets and accommodating substantial increase in bucket size and capacity.

Other object and advantages of the invention will become apparent in the following detailed description of preferred embodiments of the invention.

Now, in order to acquaint those skilled in the art with the manner of making and using the improved buckets of the invention, I shall describe, in connection with the accompanying drawings, preferred embodiments of the invention and preferred maners of making and using the same.

In the drawings:

Figure 1 is a side view of a wheel excavator of the character to which the invention relates;

Figure 2 is a side elevation, on an enlarged scale, of the excavator wheel;

Figure 3 is a fragmentary bottom view of the wheel on a still larger scale, the view being taken substantially on line 3-3 of Figure 2 and showing one embodiment of the improved bucket of the invention;

Figure 4 is a longitudinal vertical section of the bucket taken substantially on line 4-4 of Figure 3;

Figure 5 is a botom view of a wheel, similar to Figure 3, showing a second embodiment of the bucket, the view being taken substantially on line 55 of Figure 6;

Figure 6 is a vertical longitudinal section of said second embodiment taken substantially on line 66 of Figure 5; and

Figure 7 is a transverse vertical view of said second embodiment showing the wheel and part of one bucket in section and the remainder of the bucket in front elevation.

Referring now to the drawings, and particularly to Figures 1 and 2, the excavating apparatus to which the invention relates is shown as including a base It) mounted on four sets of double Caterpillar treads 11 for self propelled movement. The base carries a horizontally swingable carrier 12 including a superstructure 13 which houses part of the operating equipment of the apparatus. The carriage also mounts a pair of booms or gantrys 14 and 15 and a pair of ladders 16 and 17 which, respectively, are supported by the gantrys for arcuate movement in a vertical plane. The ladder 16 is mounted for extensible and retractable movement relative to the carriage and at its outer end supports a digging wheel 18 mounted for rotation about a horizontal axis.

The wheel 18 carries a'plurality or" circumferentially spaced buckets 19 at its periphery, which buckets are adapted to dig into and scoop up earth. The wheel is closed at one side by a vertical wall and is open at its other side. A conveyor 20 (Fig. 2) is mounted on the ladder 16 to the open side of the wheel and parallel thereto for carrying material excavated by the buckets rearwardly along the ladder. At the rearward end thereof, the ladder 16 and conveyor 20 extend over the ladder 17 so that material moving oil the conveyor 20 falls onto a similar conveyor mounted on the ladder 17, which conveyor in turn carries the earth to the outer end of the ladder 17 to stack the same on a spoil bank 58.

The apparatus is entirely self motivated and includes means for actuating the treads 11, for rotating the wheel, for moving the two conveyors, for raising and lowering the outer end of each ladder, for extending and retracting the digging ladder and for swinging the carriage horizontally.

In use, the wheel excavator creates and works in the environment diagrammatically shown in Figure l. The apparatus rides upon the surface of an exposed seam of coal or the coal vein CV with its digging ladder 16 extending in the general direction of continuation of the seam and with its stacker ladder 17 extending over an area from which the coal has been removed. With the wheel 18 rotating, the carriage 12 is swung in an arc to move the ladder 16 and wheel 18 horizontally across the face of the high wall HW, the ladder being extensible and retractable to engage the wheel to the proper extent in the wall. As the wheel is moved horizontally the buckets 19 are rotated into and upwardly with respect to the face of the high wall to scoop up earth, whereupon the buckets carry the excavated earth upwardly. To prevent premature discharge of the earth, a stationary plug 21 (Fig. 2) is carried by the ladder 16 in cooperative relation to the wheel. As the buckets pass the upper edge of the plug 21, the earth therein gravitates downwardly onto means, such as roller means 22, in the interior of the wheel which directs the excavated earth laterally onto the conveyor 20. The conveyor 20 carries the material rearwardly and transfers it to the stacker ladder conveyor which in turn deposits the earth on the spoil bank SB in an area from which the desired coal has been removed.

The digging ladder, being extensible and movable in horizontal and vertical paths, operates over a large portion of the high wall and is effective to remove a wide horizontal strip of overburden to a substantial depth on the continuing portions of the coal vein. The wheel excavator works in tandem with a conventional shovel (not shown), such as a 30 cubic yard shovel, which removes the remainder of the overburden. In the meantime, a smaller shovel (not shown) works on the strip of exposed coal lying between the excavator and the spoil bank. After the coal is removed, the shovel spoil is stacked onto said strip, while the stacker ladder 17 extends over and beyond the said strip to stack its spoil on top of the shovel spoil in one or more preceding strips. This affords the distinct advantage that the upper strata of overburden, principally soil, are redeposited on top of the lower strata of overburden, which are principally rock and sha-le, so that the area from which the coal has been removed can be reclaimed for farming or the like.

When the wheel excavator and shovel have performed their work on one strip and have moved horizontally to the side edge of the coal seam or the boundary of the mine, the two are moved into position on top of the exposed coal in the newly finished strip and commence work on a further strip as they are moved back across the vein. The smaller shovel continues to remove the coal and make room for the overburden spoils of said further strip. Thus, the wheel excavator and shovel employ the coal seam as their roadway, and the three forms of apparatus, as they perform their work in the manner defined, operate in a self created ditch between the high wall and spoil bank and progressively advance the ditch along the country side, constantly filling in the ditch behind them.

The wheel excavator is particularly intended for use in areas of 40 to foot overburden. In the illustration of Figure l, the wall HW would be about 80 feet high, a quite frequently encountered condition. It would be impractical to attempt removal of that amount of overburden with conventional drag lines and shovels. The wheel excavator, however, is capable of efficiently removing overburden of the stated depth. To do so, the excavator is mammoth, embodying a superstructure 13 about 35 feet wide, 50 feet long and 4 to 5 stories high, a gantry structure extending feet in the air, a digging ladder 81 feet long and extensible and retractable in approximately a 50 foot stroke, and a stacker ladder 250 feet long. The wheel 18 normally carries eight buckets and, with conventional buckets, is 20 feet in diameter.

A conventional bucket is generally beak-shaped, as shown in Figure 2, and consists of a solid, arcuate back wall, solid side walls and a toothed cutting lip at the leading end of the back and side walls. In a conventional design, the rim diameter of the wheel is 16 feet. The lip of each bucket projects two feet beyond the wheel rim, and the tail extends slightly less than two feet inwardly from the rim. The back wall of the bucket is formed on the smooth are of a quarter circle having a four foot radius, the back wall and lip being about 8 feet long. The distance between the side walls is 2% feet. The plug 21 complements the buckets and includes a base wall spaced about two feet inwardly of the wheel rim to accommodate passage of the bucket tail. The plug also includes a radial wall closing a portion of the wheel to the open side thereof. Each bucket 19, as it cuts into the overburden, moves into the plug 21, so that the effective vertical area of the bucket comprises a segment of a circle having about a four foot radius and a peripheral arc of approximately 8 feet. The theoretical volume of each bucket thus is over 1 /2 cubic yards. The wheel is rotated at 8 to 10 R. P. M., and theoretical excavating capacity is about 7500 cubic yards per hour. However, due to the manner of use thereof, the buckets, even when clean, cannot fill entirely on each wheel rotation and the effective capacity of a clean bucket is considerably less than theoretical.

Specifically, horizontal swing speed is 40 to 61 F. P. M., so that each bucket is entered into a fresh cut to an extent less than full bucket width. At the upper limits of 10 R. P. M. and 61 F. P. M., each bucket effects a cut three-quarter foot wide. Wheel diameter is feet and the cutting arc is approximately one-third of a circle, so that cut height is over 15 feet. As each cut is started, wheel retract could be advanced as much as two feet, the radial extension of the bucket, so that cut depth could be as great as two feet. Effective capacity therefore should be about 0.83 cubic yards per bucket or 4000 cubic yards per hour at the upper limits of operational speeds. At the lower limits, effective capacity should be about 0.74 cubic yard per bucket or 2800 cubic yards per hour.

However, due to mechanical limitations, the buckets cannot continually be advanced into the overburden in the manner described. When starting a cut, the arc of swing is short and the out less at the ends of the arc. At each end of the swing, there is certain delay in reversing the direction of swing, advancing the ladder toward the bank and adjusting the ladder to proper height. The conveying system also imposes certain limitations, and there is of course the element of human error, misjudgment and/or inefficiency. Accordingly, with clean buckets of the conventional type above described, capacity is about 1200 cubic yards per hour.

With the conventional buckets, accumulation of earth on the solid walls thereof decreases average capacity and necessitates frequent manual cleaning. From one cleaning to the next, average capacity is found to be about one-sixth less than the above-indicated capacity, or only 100 cubic yards per hour, and even then the wheel must be shut down for about 60 hours per month for the purpose of manually cleaning the buckets. Obviously, the expense of the wheel excavator is great. As explained, the assignee of the application, from twelve years of experience, has found the inefficiency of conventional buckets due to earth accumulation to result in a monthly loss of over $20,000.00.

The object of the invention in a sense is two-fold, first, to eliminate this excessive cost factor, and second, to increase wheel capacity beyond that even of clean conventional buckets, thus appreciably to increase the efiiciency of over-burden removal and decrease the cost of coal production. This is accomplished according to the invention by the provision of improved self cleaning buckets for the wheel. In its first aspect, the invention may involve, simply, the conversion of a conventional bucket, as shown in Figures 3 and 4, and in attainment of its full advantages, provides a new concept in bucket design, as disclosed in Figures 5 to 7.

Referring to Figures 3 and 4, a conventional bucket is shown as comprising a metallic three-walled structure, suitably a casting, including a pair of side walls 23 and a rear or back wall 24 joining the side walls. The side walls 23, as viewed in elevation, are each generally beakshaped, in the form of one-half of a crescent. The rear wall 24 is arcuate to conform to the outer peripheral margin of the side walls, and for most efiicient service comprises the arc of a quarter circle. The bucket is mounted on the wheel with the tail or pointed end thereof extending within the confines of the wheel and the leading or open end thereof extending radially beyond the periphery of the wheel. Each bucket is suitably secured to the wheel by yelding portions of the side walls to the rim 25 of the wheel and by welding the tail of the bucket to a rod 26 secured to and extending transversely of the wheel. To rigidify the wheel structure, a tie rod 27 also extends between the rims 25 rearwardly of each bucket. At the forward edge thereof, the bucket includes an outwardly flared lip 28 welded to the walls 23 and 24 of the bucket and to the wheel rims. The lip 28 provides an entry opening to the bucket and a plurality of teeth 29 are attached to the leading edge thereof to cut into and break up the earth.

According to the present invention, an aperture or opening 30 is provided in the rear wall 24 of the bucket, and the opening is closed by a perforate, flexible mat 31 mounted for movement'relative to the bucket proper. The opening 30 is preferably of a size corresponding to approximately 75% of the rear wall, and is spaced from the leading edge of the bucket so as not to weaken the lip and tooth supporting portions thereof. While I have shown the aperture or opening 30 as being provided only in the back or rear wall of the bucket, it will be apparent as the description proceeds that theopening may extend into the side walls. Thus, the converted bucket provided by the invention comprises a bucket having a generally rectangular opening in at least the back wall thereof and a perforate, flexible and movable rnat closing the opening.

The mat 31 preferably comprises a longitudinally and transversely linked chain, specifically, a plurality of longitudinally extending chains 32 joined together in the transverse direction by chain links 33 to form a generally rectangular chain mesh. As shown, the transverse links 33 are preferably disposed in alternately staggered relation between the chains 32. The mat is of a length greater than the shortest distance between the opposite ends of the opening 30 and preferably of a length to conform to the arcuate curvature of theback wall of a conventional bucket as shown. The width of the mat is less than the width of the opening for purposes to be described. The mat therefore is rectangular and of a size substantially complementary to the opening 30 in the back wall of the bucket.

To secure the chain mat to the bucket in the opening 30, a plurality of U-shaped brackets 34 are secured to the bucket at each end of the opening in spaced parallel relation with the bight portion of the U spaced from the edge of the opening. The legs of each bracket engage the opposite surfaces of the bucket and are secured thereto, suitably by welding. The bight portions of the U- shaped brackets comprise hinge leaves or the like adapted for the reception and support of a mounting rod or pintle pin 35 at each end of the opening. The end links of the chains 32 are inserted between the brackets 34 and the pins or rods 35 are passed through the brackets and links pivotally to secure the chain mesh to the bucket within the opening 30. If desired, the pins 35 may suitably be secured to the respective brackets 34, as by welding. The chain mat is not connected to the bucket at the sides of the opening 30 so that the same will have freedom of movement in response to actuation of the wheel. Thus, the chain mat is freely spaced at all four edges from the margins of the opening in the bucket, and is pivotally mounted solely at its forward and rearward edges to the bucket. Of particular importance is the fact that the mat as thus mounted neither overlies nor underlies any part of the bucket proper.

In use of the converted bucket, as the bucket moves downwardly and forwardly toward excavating position, the chain mat 31 gravitates freely downwardly to commence assuming the general arcuate curvature of the remaining portions of the back wall 24 and the peripheral edges of the side walls 23. As the bucket is initially forced into the earth, the mat is effectively restrained only at its leading edge and is therefore free to assume a contour most effective for carrying the load of earth to be materials such as sand. The bucket then moves upwardly and passes over the upper edge of the plug 21, Whereafter the earth and the chain mat commence gravitating downwardly to discharge the earth from the bucket. Adherence of the earth to the chain at this stage is not detrimental since the chain moves therewith and the perforate nature of the mat prevents the occurrence of a discharge retarding vacuum or suction force.

As gravitation continues, the mat falls a substantial distance downwardly into the bucket due to its excess length in relation to the distance between the opposite ends of the opening 30. The chain, being heavy and moving with the discharging earth through a substantial distance, attains appreciable momentum. Suddenly, the mat is stopped short due to the mounting of its ends, whereupon it automatically rebounds sharply upwardly. The shock frees the chain from the earth and permits the earth to fall into the bucket onto the means 22 and conveyor 30 so that the earth is carried away to the stacker. As the mat rebounds upwardly, it shakes itself automatically to clean itself.

The mat is preferably formed of chains as described, is pivotally mounted solely at its ends relative to the bucket, is spaced at its edges from the edges of the opening 39 and is movable and flexible in all directions. The shaking consequent upon the described rebound thus agitates every link of the mat to insure effective cleaning. Also, the mat is responsive to wheel vibration to enhance the cleaning action.

During material discharge, the side edges of the mat, due to the weight of the mat and the gravitational infiuence of the discharging mass, are moved with substantial force relative to the side walls 23 of the bucket to effect a scraping or cleaning action relative thereto.

Moreover, as the mat rebounds upwardly in the manner described, and as it again moves into excavating position, it is free to move, and to flex and sway through the opening in the back wall of the bucket to clean the edges of the opening and prevent excess accumulation of earth on the bucket surfaces.

The fact that the mat neither overlies nor underlies any surface portion of the bucket proper is of utmost importance in assuring continuance of the described selfcleaning action. Specifically, the bucket is moved with such force and impact into the earth that solid masses of earth are repeatedly rammed and forcibly packed into the bucket. If the mat rested on or cooperated with an overlying surface of the bucket, the sticky earth materials would effectively glue or fasten the chain to the overlying bucket surfaces. This could prevent discharge of all but a minor fraction of the mass of earth, and the earth remaining in the bucket would cover the mat and render the same inflexible and immovable, whereupon the bucket would be no better than a dirty conventional bucket. Initially, the earth packed into the bucket might confine only the edges of the mat to the overlying bucket surfaces. That would restrict mat movement, it accommodating any movement, prevent thorough cleaning of the bucket and form an adherent mass in the bucket facilitating further accumulation of earth therein. As earth accumulated in the bucket, the mat would be subjected to a creeping paralysis eventually rendering the mat totally ineffective and rendering the bucket no better than a conventional one. On the other hand, if the mat were to overlie any portions of the bucket, mat movement would be so severely restricted as to prevent attainment of the above described functions. Accordingly, it is apparent that the specified mounting of the mat enhances and insures self-cleaning.

In view of the foregoing, it is to be appreciated that the mat, in keeping itself clean and effecting a scraping action relative to the side walls, prevents excess accumulation of earth on the bucket surfaces. Some earth, of course, may accumulate on the side walls, but the thickness of the accumulation normally will not exceed the spacing between the side walls and the side edges of the mat. The slight accumulation permitted would not reduce effective bucket capacity, since the volume of the bucket would still appreciably exceed the volume of earth cut by each bucket on each wheel rotation. Therefore, the invention eliminates the predominant disadvantages of previously known buckets, namely, the problem of constantly decreasing capacity and the need for frequent shut-down of the excavator to accommodate manual cleaning of the buckets. By virtue of elimination of the two disadvantages, the actual capacity of clean buckets (1200 cubic yards per hour in the example given) is constantly maintained, thereby to increase peak efliciency operating time of the excavator by or more hours per month. Based on actual experience, the excavator described, prior to incorporation of the buckets of the present invention, had an average monthly operating time of about 420 hours. Operation however was at fivesixths of clean bucket capacity or the equivalent of about 350 hours of full capacity operation. The present invention, by increasing efiiciency and eliminating shut-down time has increased the full capacity operating time to 480 hours. The present invention therefore, simply by conversion of conventional buckets, and though directed solely to improvement of the buckets in the mammoth machine described, a dimensionally infinitesimal part of the whole, increases the usefulness and monthly capacity of the excavator by 40% or more.

However, even this remarkable advance does not constitute the end limitation of the present invention. Quite to the contrary, since the chain mat renders the bucket self-cleaning, the bucket of the invention is not restricted to the design limitations of conventional buckets. Specifically, in an endeavor to render conventional buckets as efiicient as possible, the back wall of the bucket must comprise the smooth arc of a quarter circle. According to the present invention, this restriction is abolished and a new design is evolved wherein the curve of the back wall is more abrupt, and the radial extension and width of the bucket are substantially increased over that conventional for a given wheel rim diameter and a given circumferential bucket spacing, substantially to increase effective bucket capacity.

An improved self-cleaning bucket constructed basically in accordance with the present invention is shown in Figures 5 to 7. The bucket is assembled directly on the wheel and is comprised essentially of four components, a lip 40, side walls 41, a tail 42 and a chain mat 43. As previously described, the wheel includes spaced parallel rims 25 and a plurality of circumferentially spaced rods 27, one to the rear of each bucket, tying the rims together. One side of the wheel is closed by a vertical wall and the other side is open to accommodate lateral discharge of material to the digging ladder conveyor.

The lip 40 is generally U-shaped and includes widely spaced sides or legs 44 of substantial length, an arcuate back or bight portion 45 and arcuate corner portions joining the legs 44 to the opposite sides of the back 45. The lip is preferably formed of rolled steel and the leading portions thereof are flared outwardly to funnel earth into the bucket. At the leading edge of the back and at the said arcuate corners between the back and sides, the lip is provided with spaced recesses within which tooth mounting plates 46 are welded. A hard steel cutting tooth or tip 47 is detachably secured to each plate 46, suitably by bolts. Each tooth is flared outwardly at its sides and is recessed at its upper surface rearwardly of the cutting edge to effect an efficient cut. Atits inner end, each tooth is bifurcated to fit over its mounting platev and facilitate attachment of the tooth thereto. The lip 40 of each bucket, at the ends of its sides 44, is welded to the rims 25 of the wheels adjacent but rearwardly of one of the tie rods 27 in such manner that the leading edge of the lip extends radially of the wheel. The end of the side 44 to the open side of the wheel flares outwardly of the rim, and a supporting bracket 48 is welded to the outer side of the rim to afford full support for the lip.

The side walls 41 of the bucket are formed separately of one another, there being a left hand wall and a right hand wall of the same essential structure. Each wall comprises three principal parts, an inner generally radial base plate 49, an outer inclined base plate 50 and a generally triangular, transversely curved apex member 51. The base plates 49 and 50 have straight upper edges engaging one another and are welded together at said edges. Generally triangular reenforcing bars 52 are welded between the plates to rigidify the same. The apex member 51 adjacent its radially outward edge is curved transversely inward with respect to the wheel to conform the peripheral portion of each side wall to the curvature of the adjacent portion of the lip 40. The base edge of the member 51 complements the upper edges of the plates 49 and 50 and is welded thereto. The resulting composite wall is welded at its leading edge to the trailing edge of the side 44 of the lip, and at the inner edges of the base plates 49 and 50 is welded to the respective rim 25 of the wheel, the inner edges of the plates conforming to the arcuate curvature of the rim. Each wall has a radial dimension substantialy less than that of the lip, and the length of the side wall in relation to its radial dimension appears relatively short. However, the circumferential extent of the side wall is at least equal to the circumferential dimension of the side wall of a conventional bucket, and the illusion of shortness is the consequence of substantial increase in the radial dimension of the bucket.

The tail portion 42 of each bucket is likewise a composite assembly which is welded to the radially inward surfaces of the wheel rims 25 generally as a continuation of the side walls 41. The tail includes a pair of generally triangular side wall structures 53 each including spaced parallel radial walls 54, end closures 55 and transverse reenforcing bars 56. The base of each triangular structure 53 is welded to the inner surface of the respective rim, with the leading leg thereof generally comprising a continuation of the side wall 41 and the trailing leg thereof extending'beneath the lip 40 of the next adjacent bucket. At the apex of the leading and trailing legs of the two structures 53, a large diameter reenforcing bar 57 is extended transversely between the two structures to rigidity the same and to rigidify the wheel and the lip of the adjacent bucket. The bar is preferably welded at its ends in the said structures. A generally U-shaped plate 58 of a length equal to the distance between the side structures 53 is slipped over and welded to the bar 57 with the plate portion disposed to the leading side of the bar aligned with the terminal edges of the side walls 41. The plate 58 is also welded to the walls 54 of the structures 53 and the open end thereof is closed by a plate 59 welded to the free ends of the legs of the U, the plate 59 preferably being inclined relative to the said leading plate portion of the member 58. The plates 58 and 59 thus comprise the tail portion of the back wall of the bucket.

As thus formed, the composite bucket assembly is extremely rigid and sturdy to withstand the tremendous burden imposed thereon and the abuse to which the same is unavoidably subjected in excavation of overburden containing gravel, rocks, boulders and the like. The teeth 47 are readily replaceable in the event of excessive wear or fracture.

The chain mat 43 is substantially the same as the mat 31 previously described, except that it is substantially longer and wider and constitutes a greater proportion of the back wall of the bucket. The mat 43 is rectangular and comprised of longitudinally and transversely linked chains, including longitudinally extending chains 60 and alternately staggered transverse chain links 61. The mat is longer than the shortest distance between 10 the lip and tail of the bucket and of a width slightly less than the spacing of the side walls 41. 7

At its rearward end, the mat is pivotally mounted to the bucket in spaced relation to the tail 42 by means of clips or brackets 62 and a rod or pintle pin 63. Each clip 62 comprises a generally V-shaped metal strap including a loop portion at its apex for reception of the rod 63. A plurality of the clips, one more than the number of the chains 60, are secured in spaced parallel relation to one another on the tail of the bucket with the legs thereof welded to the plates 58 and 59 of the tail and with the loops thereof aligned with one another in spaced parallel relation to the leading edge of the tail. The end link of each chain is inserted between a pair of the brackets 62 and the rod 63 is then passed through the loops and end links pivotally to mount the chain mat at its rearward edge in spaced relation to the bucket tail. The rod 63 is suitably a straight,.cylindrical, solid rod. To accommodate insertion and removal thereof, an opening 64 is provided in the side portion 53 of the tail at the open side of the wheel. The rod may be retained in position, as shown in Figure 7, by spot welding the same to one or more of the clips 62.

At its forward edge, the chain mat 43 is pivotally mounted in spaced relation to the lip 40 of the bucket by a mounting structure indicated generally at 65. The structure includes an arcuate strap 66 complementary to the trailing edge of the back of the lip 40, a plurality of clips or brackets 67 and a rod or pin 68. The clips 67 each comprise a generally U-shaped metal strap, and the clips are of progressively decreasing length from the center to the sides of the bucket lip. The clips are welded at their free ends to the strap 66 in spaced parallel relation to one another to define a curved path for reception of the rod 68, the defined path having curvature both longitudinally and radially of the bucket. After the clips have been welded to the strap 66, the strap may be welded to the trailing edge of the back of the lip 40. The rod 68 in turn is complementary to the defined path so as to be insertable within the clips 67. The end links of the mat at the forward edge thereof are inserted between the clips 67, and the rod is passed through the clips and end links pivotally to mount the chain mat at its forward edge in rearwardly spaced relation to the bucket lip. The rod 68 due to its curvature imparts a concave or transversely dished configuration to the inner surface of the mat at least at the forward portions thereof to conform the mat to the curvature of the lip. Also, the curvature of the rod holds the side chains closer to the lip to maintain a uniform longitudinal disposition of the chains 60 despite the concavity of the mat. The curved rod thus imparts to the chain a configuration substantially duplicating the configuration the back wall of the bucket would have if the back wall were solid. In addition, the rod 68 disposes the chain in arcuate alignment with the curved apex members 51 of the bucket side walls 41, thus to afford a highly efiicient bucket construction. The rod may be spot welded in place to one or more of the clips 67.

The chain mat 43 is thus detachably mounted on the bucket, and the same is readily removed to accommodate repair or replacement simply by removing the rods 63 and 68.

In use of the bucket disclosed in Figures 5 to 7, the functions of the bucket and chain mat are substantially the same as previously described with respect to Figures 3 and 4. As the bucket is initially forced into the earth, the mat is free to assume the contour most effective for carrying the load of earth to be forced into the bucket. Subsequently, the chain mat insures complete discharge of the earth therein as the bucket reaches discharging position, the mat at that time gravitating downwardly to a substantial extent into the bucket to attain appreciable momentum. When the mat is stopped short due to the mounting of its ends, it automatically rebounds sharply upwardly to free the excavated earth therefrom and to shake itself, whereby the earth is fully discharged and'the mat cleans itself. Also, as the mat gravitates into the bucket, the side chains effect a scraping action relative to the side walls 41 of the bucket to prevent excess accumulation of earth thereon. The chain mat neither overlies nor underlies any of the solid wall portions of the bucket, and therefore is not subject to being rendered ineffectual. The mat is free to sway and flex beyond the peripheral margins of the remainder of the bucket to insure thorough cleaning of the chains and the bucket components. Since the mat constitutes substantially the entirety of the back wall of the bucket, and since the side edges thereof are disposed closely adjacent the side walls 41 of the bucket, the chain mat maintains substantially complete theoreticalbucket volume at all times.

The advantages of the bucket disclosed in Figures to 7 over that disclosed in Figures 3 and 4 reside principallyin the very substantial increase in bucket size and capacity afforded according to the invention. The bucket is of considerably greater height and width than a conventional bucket, its back wall is longer, deeper and more abruptly curved, and the average height of the side walls is greater than could be possible with conventional buckets. In a preferred embodiment, the improved bucket of the present invention may be mounted on a wheel having a rim diameter of 16 feet. In such size, wheel capacity can be directly contrasted to that of the previously described embodiment of the invention. The resultant wheel construction has a rim diameter of 16 feet and the wheel carries eight buckets. With the improved buckets of the invention, bucket height at the trailing edge of the lip is 3 feet, the length of the bucket wall is 9 feet and bucket width is over 3% feet. The volume of each bucket as it moves through the plug 21 is about 3 cubic yards. Theoretical excavating capacity for the wheel, when operating at 10 R. P. M., is about 15,000 cubic yards per hour.

Theoretical capacity, of course, is not obtained in practice, but the increased size, width and capacity of the improved bucket will, when embodied in a complete machine of sufficient strength and having adequate power supply and material conveying capacity, accommodate such increases in swing speed, depth of cut and peak bucket capacity that effective excavating capacity should attain more closely to theoretical than could be posible with conventional buckets. Specifically, in this regard, the significant improvements provided by the present invention are an entirely self-cleaning bucket of constant peak capacity and increased height, whereby, in the stated example, wheel diameter is increased to 22 feet, the cutting height is increased to over 16 feet, and the depth of cut can be increased to three feet.

In actual use, the assignee of the application has thus far been restricted to use of the wheel described above on an existing wheel excavator equipped with the drive mechanism and conveyor system for a conventional bucket wheel. Even within the limitations of the existing equipment, the improved buckets of Figures 5 to 7 have substantially doubled excavating capacity while appreciably reducing operating speeds, thereby decreasing the abuse to which the excavator and all of its components are subjected and increasing excavator life and operating time. Specifically, with the wheel above described in conjunction with Figures 5 to 7, the wheel is rotated at about 6-7 R. P. M., swing speed is approximately 40-45 F. P. M. and the buckets are advanced about 1 /2 to 2 feet into the bank at the end of each swing. When operated at these speeds, the wheel provides, with case, an actual output of approximately 1900 cubic yards per hour.

From the foregoing, it is to be appreciated that the present invention, simply by improving upon the buckets of wheel excavators, an infinitesimal part of the whole,

is capable of rendering an existing excavator abopt twice as effective as was heretofore possible. By conversion of a conventional bucket, the present invention, per month, affords a production increase of over 150,000 cubic yards of overburden, effectively increases operating time by hours or more, and saves over $20,000.00 in coal production. In its preferred embodiment of Figures 5 to 7, the present invention increases monthly output over conventional buckets by almost one-half million cubic yards, thus to effect a monthly saving in coal production of more than $60,000.00.

While I have shown and described what I regard to be preferred embodiments of my invention, it will be apparent that various changes, rearrangements and modifications may be made therein without departing from the scope of the invention, as defined by the appended claims.

I claim:

1. A self-cleaning digging wheel bucket for excavating apparatus comprising a bucket including spaced parallel side walls each having a generally arcuate peripheral edge, a lip portion bridging between the peripheral edges of said side walls at the leading edges thereof, a tail portion bridging between the peripheral edges of said side walls at the trailing edges thereof, said peripheral edges and said lip and tail portions defining an opening, and a perforate flexible mat for said opening extending between said lip and tail portions, said mat being of a width less than the distance between the peripheral edges of said side walls and of a length substantially greater than the shortest distance between said lip and tail portions, said mat being hingedly connected to the bucket at its forward edge in rearwardly spaced relation to the trailing edge of said lip portion and at its rearward edge in forwardly spaced relation to the leading edge of said tail portion, said mat at the side edges thereof being freely spaced from and freely movable with respect to said side walls, said mat being flexible in all directions and freely movable into and out of said opening.

2. A self-cleaning digging bucket for rotatable excavating wheels comprising spaced parallel side walls each having a generally arcuate peripheral edge extending inwardly with respect to the wheel from the leading to the trailing ends thereof in the direction of wheel rotation, a lip portion joining the peripheral edges of said side walls at the leading ends thereof, a tail portion joining the peripheral edges of said side walls at the trailing ends thereof, said peripheral edges and said lip and tail portions defining an opening and a long flexible mat extending between said lip and tail portions, said mat being disposed in said opening and connected solely at its forward and rearward edges with respect to the remainder of the bucket, said mat being hingedly connected at its forward edge in rearwardly spaced relation to the trailing edge of said lip portion and at its rearward edge in forwardly spaced relation to the leading edge of said tail portion, said lip and tail portions and said mat comprising the back wall of the bucket with said mat constituting the greater portion of the back wall, said mat being of a width less than the distance between said side walls and being freely spaced from and freely movable with respect thereto, said mat being flexible in all directions and of a length substantially greater than the shortest distance between said lip and tail portions, said mat being freely movable into and out of said opening, said mat when the bucket is disposed with its back wall down freely gravitating peripherally outward of the space between said side walls and generally into conformity with the peripheral edges of said side walls, said mat when the bucket is disposed with its back wall up freely gravitating a substantial distance downwardly between said side walls to discharge dirt, mud, clay and the like from the bucket and said mat and to effect a scraping action relative to said side walls to clean the same, said mat being of substantial weight and attaining substantial momentum upon gravitational movement thereof to rebound sharply from its lowest position of movement and shake itself clean.

3. In a digging wheel bucket having at least part of the back wall thereof open and a flexible mat mounted in the opening, the improvement comprising a mat consisting of a large number of parallel chains disposed closely adjacent one another and a plurality of transverse chain links connecting adjacent chains, said chains defining a perforate mat flexible in all directions, said mat being mounted on the bucket with the four edges thereof freely spaced from the edges of the opening in the bucket and from the bucket walls, said bucket in the area of said opening, and both inwardly and outwardly of said area, being free of obstruction except for said mat and its hinged connection, said mat being hingedly connected solely at the forward and rearward edges thereof relative to the bucket and being free of the bucket at the side edges thereof, said chains being of a length greater than the shortest distance between the mountings of said mat and being freely movable into and out of said opening.

4. In a digging wheel bucket having at least part of the back wall thereof open and including lip and tail portions at the opposite ends of the opening and a flexible mat in the opening, the improvement comprising a pair of rods mounted respectively in rearwardly spaced relation to the trailing edge of the lip portion and in forwardly spaced relation to the leading edge of the tail portion, and a large number of parallel chains disposed closely adjacent one another and defining a perforate rnat flexible in all directions, said chains extending longitudinally of the bucket between said rods and each being of a length substantially greater than the shortest distance between said rods, said rods extending transversely through the end links of each chain hingedly to mount the forward and rearward ends of the chains in spaced relation respectively to the trailing edge of the lip portion and the leading edge of the tail portion, the portions of said chains between said rods being free of the bucket, spaced from all surface portions of the bucket and not overlying or underlying any such surface portions to be freely movable into and out of the interior of the bucket.

5. A self-cleaning digging wheel bucket comprising spaced parallel side wall means of generally half-crescent form having an upstanding leading edge, a generally arcuate peripheral edge and a base edge extending between said leading edge and the trailing end of said peripheral edge, and back wall means extending between the peripheral edges of said side wall means, said back wall means including narrow lip and tail portions extending between and joined to the peripheral edges of said side wall means at the leading and trailing ends thereof respectively, a pair of rods extending between the peripheral edges of said side wall means reardwardly and forwardly, respectively, of the trailing edge of said lip portion and the leading edge of said tail portion, means connecting said rods respectively to said lip and tail portions in spaced relation thereto, a plurality of spaced parallel chains disposed closely adjacent one another and extending longitudinally of the bucket between said lip and tail portions, and a plurality of transverse chain links connecting adjacent chains, said chains and links constituting a perforate mat flexible in all directions, said chains each being of a length substantially greater than the shortest distance between said lip and tail portions, said rods extending transversely through the end links of said chains hingedly to mount the forward and rearward edges of the mat in spaced relation respectively to the trailing edge of said lip portion and the leading edge of said tail poi tion, the mat at its side edges being free of the remainder of the bucket, the outboard ones of said chains extending adjacent but in transversely spaced relation to the respective side wall means and being freely movable relative thereto, said chains and links constituting substantially the entirety of the back wall means of the bucket and being spaced from and not overlying or underlying any of the remainder of the bucket, said chains and links being freely movable with respect to said lip and tail portions and said side wall means into and peripherally outward of the space between said side wall means.

6. A digging wheel bucket comprising a pair of spaced generally parallel side walls each having a generally arcuate peripheral edge, a generally U-shaped lip secured to said side walls at the leading edges thereof, said lip including leg portions aligned with said side walls, a bight portion extending beyond the peripheral edges of said side walls and arcuate corner portions between said leg and bight portions, a tail extending between said, side walls at the trailing ends thereof, and a plurality of spaced parallel chains extending between said lip and tail in parallel relation to said sidewalls, said chains being of a length greater than the shortest distance between said lip and tail and being hingedly mounted at the leading and tailing ends thereof to said lip and tail respectively, the portions of said chains between said lip and tail being free of the bucket and freely movable relative to said side walls, lip and tail to define a flexible movable chain mat, the side edges of said mat as comprised of the outboard ones of said chains being disposed closely adjacent but spaced from the respective one of said side walls and being freely movable relative thereto, the chains adjacent the side edges of said mat having in effect less slack between said lip and tail to be disposed adjacent and conform generally to the peripheral edges of said side walls, said chains each comprising a continuation of the part of said lip to which connected to constitute a perforate, flexible, somewhat transversely dished back wall to the bucket conforming generally to the arcuate curvature of the peripheral edges of said side walls when the bucket is disposed right side up, said chains, when the bucket is disposed upside down, gravitating freely into the space between said side walls to discharge the contents of the bucket.

7. A digging wheel bucket comprising a spaced generally parallel side walls having an upstanding leading edge and a generally arcuate peripheral edge, each of said side walls adjacent said edges having a transversely curved inwardly extending portion, a generally U-shaped lip secured to said side walls at the leading edges thereof, said lip including leg portions aligned with said side walls and an arcuately curved bight portion aligned in part with said portion of said side walls and extending beyond the peripheral edges of said side walls, a tail extending between said side walls at the trailing ends there of, a plurality of spaced parallel chains extending between said lip and tail in parallel relation to said side walls, and a plurality of transverse chain links connecting adjacent ones of said chains, said chains being of a length greater than the shortest distance between said lip and tail and being hingedly mounted at the leading and trailing ends thereof to said lip and tail respectively, the portions of said chains and said chain links between said lip and tail being free of thebucket and freely movable relative to said side walls, lip and tail to define a flexible movable chain mat, the side edges of said mat as comprised of the outboard ones of said chains being disposed closely adjacent but spaced from the respective side wall and being freely movable relative thereto, said chains from the side edges of said mat to the center thereof being hingedly connected to the trailing edge of said bight portion of said lip in progressively increasing rearwardly spaced relation to said trailing edge to have in effect progressively increasing slack between said lip and tail, said chains each comprising a continuation of the part of said bight portion of said lip to which they are connected to constitute a perforate flexible transversely dished back wall to the bucket conforming generally to both the arcuate curvature of the bight portion of said lip and the arcuate curvature of the peripheral edges of said side walls when the bucket is disposed right side up, said chains, when the 'bucket is disposed upside down, gravitating freely into the space between said side walls to discharge the contents of the bucket.

8. A bucket for rotatable digging wheels having a pair of spaced parallel rims, comprising a tail fixedly secured to said rims radially inwardly thereof; a pair of side walls secured respectively to said rims and extending radially outwardly therefrom, each of said side walls having a generally arcuate peripheral edge; a generally U-shaped lip having radially outwardly extending leg portions and an arcuate bight portion, said leg portions being aligned and secured at the trailing edge of the lip to the leading edges of said side walls and being secured at the ends thereof to said rims, said bight portion extending radially beyond the peripheral edges of said side walls, said lip being flared outwardly from the trailing to the leading edges thereof; a curved rod mounted on the trailing edge of said bight portion of said lip and extending from one side wall to the other, said rod from the ends to the center thereof being disposed in progressively increasing rearwardly spaced relation to the trailing edge of said bight portion of said lip; a second rod mounted on the leading edge of said tail in forwardly spaced relation thereto and extending from one side wall to the other; and a chain mat comprising a plurality of longitudinally extending spaced parallel chains and a plurality of transverse chain links connecting adjacent chains, said mat being of a width less than the distance between said side walls and of a length greater than the shortest distance between said rods, said chains each being hingedly mounted at the leading and trailing ends thereof on said curved and second rods respectively, said chain mat being transversely dished at least at the leading end portion thereof to conform to the bight portion of said lip and having an arcuate curvature conforming generally to that of the peripheral edges of said side walls when the bucket is disposed right side up, said mat being freely spaced from and freely movable with respect to said hp, side walls and tail to move freely into and out of the space between said side walls to accommodate and extending radially inwardly therefrom, and a narrow plate extending transversely between said side wall structures inwardly of said rims; a pair of side walls secured respectively to said rims and extending radially outwardly therefrom, each of said side walls having an upstanding leading edge and an arcuate peripheral edge aligned generally at the trailing edge thereof with the leading edge of the respective side wall structure of said tail; a generally U-shaped lip having radially outwardly extending leg portions of substantial length and a transverse bight portion, said leg portions being aligned and secured at the trailing edge of the lip to the leading edges of said side walls and being secured at the ends thereof to said rims, said bight portion extending radially beyond the peripheral edges of said side walls, said lip being flared outwardly from the trailing to the leading edges thereof, and a'plurality of spaced cutting teeth detachably mounted on said bight portion; and a chain mat comprising a plurality of longitudinally extending spaced parallel chains and a plurality of transverse chain links connecting adjacent chains, said mat being of a width less than the distance between said side walls and of a length greater than the shortest distance between said lip and tail, said chains each being hingedly mounted at the leading and trailing ends thereof on said lip and tail respectively, said chains each comprising a continuation of the part of said bight portion of said lip to which connected to constitute a perforate flexible transversely dished back wall to the bucket conforming generally to the arcuate curvature of the peripheral edges of said side walls when the bucket is disposed right side up, said chain mat, when the bucket is disposed upside down, gravitating freely into the space between said side walls to discharge the contents of the bucket.

10. A bucket for rotatable digging wheels having a pair of spaced parallel rims and circumferentially spaced means connecting the rims, said bucket comprising a tail including generally triangular side wall structures fixedly secured respectively to said rims adjacent one of said means and extending radially inwardly therefrom, and a narrow plate extending transversely between the apices of said side Wall structures inwardly of said rims; a pair of side walls secured respectively to said rims and extending radially outwardly therefrom, each of said side walls comprising a composite assembly having an upstanding leading edge, an arcuate peripheral edge and a transversely curved inwardly extending portion adjacent said edges, the peripheral edge of each side wall at the trailing edge thereof being aligned generally with the leading edge of the respective side wall structure of said tail; a generally U-shaped lip secured to said rims adjacent the next adjacent one of said means, said lip having radially outwardly extending leg portions of substantial length and an arcuate bight portion, said leg portions being aligned and secured at the trailing edge of the lip to the leading edges of said side walls and being secured at the ends thereof to said rims, said bight portion being aligned with and secured to said transversely curved portions of said side walls and extending radially beyond the peripheral edges of said side walls, said lip being flared outwardly from the trailing to the leading edges thereof, said bight portion having a plurality of spaced tooth sockets therein at the leading edge of said lip, a mounting plate secured in each socket and a cutting tooth detachably mounted on each plate; a curved rod mounted on the tailing edge of said bight portion of said lip and extending from one side wall to the other, said rod from the ends to the center thereof being disposed in progressively increasing rearwardly spaced relation to the trailing edge of said bight portion of said lip; a straight rod mounted on the leading edge of said plate of said tail in forwardly spaced relation thereto and extending from one side wall to the other; and a chain mat comprising a plurality of longitudinally extending spaced parallel chains and a plurality of transverse chain links connecting adjacent chains, said mat being of a width less than the distance between said side walls and of a length greater than the shortest distance between said rods, said chains each being hingedly mounted at the leading and trailing ends thereof on said curved and straight rods respectively, said chain mat being transversely dished at the leading end portion thereof to conform to the bight portion of said lip and having an arcuate curvature conforming generally to that of the peripheral edges of said side walls, said mat being freely spaced from and freely movable with respect to said lip, side walls and tail to move freely into and out of the space between said side walls.

11. In a digging wheel bucket having spaced generally parallel side walls, a lip portion adjoining said side walls at the lip end thereof and a tail portion joining said side walls at the tail end thereof in spaced relation to said lip portion, said side walls and lip and tail portions defining an opening, the improvement comprising a flexible mat hingedly connected solely at its forward and rearward edges to said lip and tail portions respectively and constituting the greater portion of the back wall of the bucket, said mat being of a width substantially the width 17 of said opening and of a length substantially greater than the straight line distance between said lip and tail portions and being freely movable into and out of said opening.

References Cited in the file of this patent UNITED STATES PATENTS 885,049 Holcomb Apr. 21, 1908 18 Cross Apr. 25, 1911 Miller Sept. 18, 1934 Stevens Mar. 25, 1947 Aisthorpe Mar. 21, 1950 Chimani Aug. 4, 1953 FOREIGN PATENTS Great Britain of 1907 U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION- Patent N0a 2,834,127 Frank F0 Kolbe May 13, 1958 It is hereby certified that error appears .in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 13, line 61, for "reardwardly" read --rearWardly-"--; column 14 line 27 and column 16, line 45, for "tailing" read trailingcolumn 16, line 68, for "adjoining" read --joining-- Signed and sealed this 1st day of July 1958,.

(SEAL) Attest: KARL H, AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

